Arrggghh! I had a whole reply that disappeared when the forum freaked out. :doh: So here we go again...

Cut the yarn about 6-8 inches or so and thread it through a yarn needle (blunt tip). Slip the needle through the stitches on the needle and remove the needle. Now cinch the yarn up and then slip it through the stitches again and weave in the end. Here's a tutorial on weaving in ends.http://www.knitty.com/ISSUEfall04/FEATfall04TT.html

You might want a tail about 12 inches or so to leave enough for seaming. But yeah, thread the tail through the sts on the needle like a drawstring, I usually do it twice, then use the rest of it for the seam.

What Jan and Sue said about the top. It's like tying up the drawstring on a laundry bag.

As for sewing the seam, use the mattress stitch. (There's a video here showing how to do it.) Next time you make a hat, do it in the round on a circular needle and you won't have to bother with the seam. Once you've knit the cylinder and tied off the top, you're done.